Electromagnetic control device



July 21, 1942. w, L, BUTLER 2,290,632

ELECTBQMAGNETIC CONTROL DEVICE Filed June 18, 1941 2 Sheets-Sheet 1 l ll Fl Fl %.3. 35

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b JAM/M His Attorney y 1942- w. L. BUTLER ELECTROMAGNETIC CONTROL DEVICE Filed June 18, 1941 2 Sheets-Sheet 2 Fig. 4.

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Patented July 21, 1942 2,290,632 ELECTROMAGNETIC CONTROL DEVICE William Lawrence Butler, Schenectady, N. Y., as- Signor to General Electric Company, a corporation of New York Application June 18, 1941, Serial No. 398,609

11 Claims. (Cl. 200-104) My invention relates to electro magnetic control devices and particularly to electromagnetic relays having means for insuring a predetermined pressure upon the contacts.

It is well understood that for electromagnets of the type generally used in this class of device the force of magnetic attraction between the electromagnet and its armature varies approximately inversely as the square of the distance between the electromagnct and the armature. The characteristic curve which represents this condition is of a generally hyperbolic shape. While ordinarily a tension or compression spring is used to bias the armature of a relay to its deenergized position, the dropout force of such a device is not closely matched with its pickup force because of the fact that the force exerted by a spring varies linearly with its deformation.

Another difficulty of a simple biasing spring frequently met where resiliently mounted normally closed contacts are used is that the pickup force exerted by the normally closed contacts increases as the armature approaches its deenergized position, while the force of the biasing spring is simultaneously decreasing with the effect that the resultant pressure at the normally closed contacts is frequently insufficient to prevent rebound and arcing upon drop-out of the relay.

Accordingly it is an object of my invention to provide a simple and reliable spring system for an electromagnetic control device which shall insure a predetermined and substantial pressure upon the normally closed contacts.

It is a further object of my invention to provide a spring system which shall exert upon the armature of .an electromagnet an opposing force closely approximating the increasing force of magnetic attraction as the armature moves toward its attracted position.

of a short pivot link which is arranged to engage a stop mounted upon the base, thereby to reverse the movement of the spring axis and to In carrying out my invention in connection with an electromagnetic relay having resiliently mounted normally closed contacts, I provide a helical spring connected between a pivoted armature member and the relay base in such'a way that its axis passes closely adjacent the pivot point of the armature. A; the armature moves toward its attracted position it carries with it one end of the helical spring so that the axis of the spring is moved nearer to the pivot point of the armature thereby decreasing the dropout torque exerted by the spring upon the armature. In order to prevent the spr ng from passing dead center with respect to the armature pivot point, the spring is connected to the armature by means stretch the spring as the armature completes its pickup stroke.

My invention itseif will be better understood and its objects and advantages further appreciated by referring now to the following detailed description taken in connection with the accompanying drawings in which Fig. 1 is a front ele-, vation of a control device embodying my invention; Fig. 2 is a side elevation of the device in Fig. 1- showing the armature in its attracted position; Fig. 3 is a fragmentary view similar to Fig. 2 showing the armature in its deenergized position; and Figs. 4, 5 and 6 are views similar to Figs. 1, 2, and 3, respectively, illustrating my invention in a modified form.

Referring now to Figs. 1, 2, and 3, I have shown a circuit controller mounted upon a base III of suitable insulating material. The controller itself comprises an electromagnet frame II and actuating coil l2 mounted upon the base ID, a rotatable switch shaft I 3 forming a pivotal mounting for a movable armature I4, and a contact assembly generally designated by the reference numeral l5. The shaft I3 is of rectangular cross-section and is provided at either end with journal portions l6, l1 seated'in fixed bearing brackets l8, l9, respectively, to form a fixed pivot. Mounted upon the shaft I3 are a plurality of leaf springs 20 carrying at their ends normally closed movable contacts 25 arranged to engage fixed contacts 26 when the switch member including the'shaft l3 and the armature i4 is in its deenergized position, The contacts 25 are connected to terminals in the base ID by means of flexible strips 21 of conducting material. Similarly mounted upon the switch shaft l3 are a plurality of leaf springs 28 carrying at their ends normally open movable contacts 29 'arranged for engagement with cooperating fixed contacts 30 when the switch member is inits attracted position. The movable contacts 29 are connected to terminals in the base") by means of fiexible'strips 3| of conducting material. 2

The brackets I8 and I9 and the switch shaft l3 form a fixed pivot for the ,switch'member comprising the contact members 20 and and the armature l4. As best shown at Figs. 2 and'3, the armature I4 is connected to an upwardlyextending arm 32 mounted upon the rectangular switch shaft I3. The upper end of the arm 32 is provided with a bumper 33 arranged to engage a stop 34 fixed to .the base' l0 thereby to determine the deener gized position of the movable switch member. The overhanging stop 34 serves also as a support for a depending U shaped coil holder 35. The lower ends of the U-shaped coil holder 35 engage the actuating coil l2 to hold it in position upon the central leg of the E-shaped core H.

In order to bias the pivoted switch member to its deenergized position and to overcome the closing force of the leaf springs 20, a helical spring 40 is connected between the switch member and a fixed bracket 4| in such a way that its axis passes closely adjacent the center of the switch shaft l3. In particular the upwardly extending arm 32 carries a protruding bracket 42 to which is pivotally connected at downwardly extending link 43. The upper end of the helical spring 40 is pivotally connected to the lower end of the pivoted link 43 by means of a connecting rod 44. Similarly, the lower end of the helihelical spring 40 closer to the center of the switch shaft l3 thereby to diminish the torque arm between the spring 40 and the movable switch cal spring is pivotally connected to the fixed bracket 4| by means of a connecting rod 45. As may now be best observed by a comparison of Figs. 2 and 3, a stop fixed to the base in is arranged to engage the pivoted link 43 after the switch member and the armature l4 have completed a predetermined portion of the pick-up stroke, thereby to prevent the helical spring 40 from passing dead center with respect to the shaft l3 and to increase the drop-out force applied by the spring to the switch member. Preferably the stop 50 engages the link 43 when the switch member has completed approximately onehalf its travel. In order to lock the movable switch member in its actuated position independently of the electromagnet ll, l2, the armature supporting arm 32 carries a depending extension 5l-, the lower end of which is connected to a bracket 52 on the base In by means of a pair oi toggle links 53, 54. The toggle 53, 54 is held in locked position by engagement of the link 54 with a fixed adjustable stop screw 55 sup-,

ported on a bracket 56 mounted on the base In.

The bracket 56 also serves as a support for a tripping magnet 51. The plunger 58 of the tri,o-,

having an approximately hyperbolic characteristic to match the force of magnetic attraction as the armature approaches the core ll. With the switch member in its deenergized position the leaf springs 20 exert their maximum force tending to pick up the armature, while the helical spring 40 is in the position indicated at Fig. 3 and exerts a relatively large force opposing that of the springs 20, thereby to insure a substantial pressure upon the normally closed contacts 25, 26. Upon energization of the electromagnet l2 and consequent movement of the armature l4 toward its'attracted position the pick-up force exerted by the leaf springs 20 decreases linearly to zero at the point where the movable contacts 25 leave the fixed contacts 26. Preferably the contacts 25,. 26 disengage after the armature has completed approximately one-third of its travel.

While the pick-up force of the leaf springs 20 is diminishing the drop-out bias exerted by the helical tension spring 40 is likewise diminishing because of the fact that the movement of the switch member is bringing the axis of the Preferably the contact springs 20 and 28 are 7 so designed that during an intermediate portion of the movement of the armature neither the contacts 25 nor the contacts 29 are in engagement. I have found that the intermediate period of travel of the switch member with all contacts out of engagement may advantageously be about one-third of the total travel. During this intermediate one-third of the travel of the armature l4 the only spring force exerted upon the movable switch member is that of the helical spring 40, the axis of which continues to move closer to the center of the switch shaft l3 thereby further to diminish the drop-out force exerted by the spring and thus to diminish the resultant drop-out force. Before the resultant spring force has diminished substantially the pivoted link 43 engages the stop 50 when the armature has completed approximately one-half its stroke. Upon engagement of the link 43 with the stop 50 the link pivots about the stop thereby to move its lower end upwardly and outwardly. The stop 50 prevents the axis of the spring 40 from moving further toward dead center, while the upward and outward movement of the lower end of the link 43 stretches v the spring 40 "and causes its axis to reverse its motion and move away from dead center. thereby to increase the force applied by the spring 40 to the switch member. If desired the stop 50 can be arranged to engage the link 43 very close to its lower end thereby to minimize reverse motion of the axis of the spring 40. Such a condition has been shown in the drawings, and it will be evident that the stop 50 here acts primarily to increase the tension of the spring 40.- Thus during the intermediate portion of the travel of the armature and after the pivoted. link 43 has engaged the stop 50, the resultant drop-out bias on the armatureincreases linearly due to the stretching, and if desired the reverse movement, of the spring 40.

, When the movable switch member has completed approximately two-thirds of its movement toward its attracted position, the contacts duced by the combination of the helical spring 7 40 and the leaf springs 28 increases quite rapidly at the end of the pick-up stroke. whereby the spring force exerted upon the armature in opposition to the force of magnetic attraction increases with a-characteristic somewhat similar to the hyperbolic characteristic of the magnetic attractive force as the armature travels to its attracted position.

At Figs. 4, and 6 I have illustrated a simplified embodiment of my invention in which the toggle latch and trip magnet are omitted. In this embodiment the electromagnet frame 70 is U-shaped and mounted upon an insulating base H for cooperation with a pivotally mounted bridging'armature 12. The armature I2 is supported between a pair of upwardly extending arms 13 which are mounted upon a rectangular switch shaft 14. The shaft M is pivotally mounted at its ends in two fixed bearing brackets 75, 16 attached to the base H.

One end of the rectangular switch shaft 14 carries a plurality of normally closed contact springs 11 and a plurality of normally open contact springs 18. The contact springs i1 and I8 cooperate respectively with fixed contacts 19 and 80 mounted on the base H. For energiz'ation of the electromagnet an actuating coil 8| is mounted upon the magnetic frame 70.

In order to connect the pivoted switch member including the shaft 14, the armature 72, and the contact springs 11 and 18 to a pivotally mounted helical spring 85, a supporting arm 86 is mounted upon the rectangular shaft 14 in substantially parallel spaced relation to the armature supporting arms 13. The upper end of the arm 86 is provided with an overhanging U- shaped bracket 81, the sides of which serve as a support for a horizontal pivot pin 88. The pivot pin 88 carries a depending link 89, the lower end of which is pivotally connected to tne upper end of the helical spring 85 through a connecting rod 90. As in the modification of Figs. 1, 2 and 3, the lower end of the helical spring 85 is pivotally connected to a fixed bracket 9| on the base by means of a connecting rod 92. A stop 93 fixed to the base H is arranged to engage the link 89.

It will be readily understood from the previous description with reference to Figs. 1, 2 and 3 that in operation the helical spring 85 cooperates with the normally closed contact springs 11 and with the normally open contact springs 18 to give a resultant spring force which increases first gradually and then rapidly asv the armature moves from its deenergized position to its attracted position.

I wish to have it understood that, if desired, the normally open contact springs may be dispensed with and instead the fixed stop may be arranged to engage the pivoted link nearer to the connection of the link with the pivoted switch member, thereby to increase the upward and outward arcuate movement of the upper end of the helical spring after engagement of the pivoted link with the stop. By this means a very rapid increase of spring force near the end of the stroke may be obtained with normally open contact springs. I

While I have shown and described certain embodiments of my invention by way of illustration, many other modifications will occur to those skilled in the art. For example, while I prefer to so proportion the various parts of my control device that the armature will complete approximately one-third of its stroke with the normally closed contacts in engagement, onethird of its stroke with no contacts in engagement, and the final third of its stroke with the normally closed contacts in engagement, the pivoted link engaging the fixed stop at about the midpoint of the stroke, it will be understood that these proportions may be varied to give the most desirable results under any particular set of circumstances. I therefore wish to have it understood that I intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination an electromagnet, a movable switch member mounted upon a fixed pivot, said member including an armature arranged for movement toward and away from said electromagnet, spring means connected between said switch member and a fixed point for biasing said armature to a-position spaced from said electromagnet, the axis of said spring being arranged for arcuate movement toward said fixed pivot as said armature approaches said electromagnet thereby gradually to diminish the dropout force applied to said armature by said spring over-a predetermined initial p'-rtion of the pickup stroke of said electromagnet, and means controlled by the movement of said switch member for increasing the drop-out force applied to said armature by said spring upon completion of said predetermined portion of said pickup stroke.

'2. In an electromagnetic device, a base, an electromagnet mounted upon said base, a movable switch member mounted upon a fixed pivot on said base, said movable member including an armature arranged for movement toward and away from said electromagnet, spring means pivotally connected to said switch member and to said base, the axis of said spring means being arranged for movement toward said fixed'pivot as said armature approaches said electromagnet, and stop means operative upon partial completion of the stroke of said switch member to prevent said spring from passing dead center with respect to said fixed pivot and to increase the drop-out force applied by said spring to said armature.

v 3. In an electromagnetic control device, a base, an electromagnet mounted upon said base, a rotatable switch shaft mounted in a fixed pivot upon said base, a magnetic armature supported upon said shaft for movement toward and away from said electromagnet, a helical spring pivotally connected to said base for biasing said armature to a normal position spaced from said electromagnet, a radial arm mounted upon said switch shaft, a pivoted link for connecting said helical spring to said arm, the axis of said helical spring being arranged for movement toward said fixed pivot as said armature approaches said electromagnet, and means associated with said link for increasing the force of said helical spring during a predetermined final portion of the stroke of said armature.

4. In an electromagnetic control device, a base, an electromagnet mounted upon said base, a rotatable switch shaft mounted upon said base,

means attached to said shaft for supporting"a magnetic armature for movement toward and away from said electromagnet, a radial supporting arm secured to said shaft in substantially parallel spaced relation to said armature, said arm carrying at its end a relatively short pivoted link, a helical tension springipivotally con-, nected to said pivoted link-and to a fixed point on the opposite side of said switch shaft to bias said armature to a position spaced from said electromagnet, said supporting arm being arranged to move the axis of said helical spring toward the center of said switch shaft as said armature approaches said electromagnet, and a fixed stop mounted upon said base to engage said pivoted link after said armature has completed a predetermined portion of its travel thereby to prevent said spring from passing over dead center with respect to said switch shaft and to increase the tension of said spring as said armature completes its travel.

'5. In an electromagnetic circuit control device, an electromagnet mounted upon a base, a

magnetic armature supported upon a fixed pivot on said base for movement from a deenergized to an actuated position, a resilient contact member operatively associated with said armature, said contact member being arranged resiliently to engage a fixed contact when said armature is in said deenergized position thereby to exert a force tending to move said armature toward said electromagnet, and a helical spring associated with said armature to overcome the force exerted by said contact member and to bias said armature to said deenergized position, the axis of said spring being arranged for movement toward said fixed pivot as said armature approaches said actuated position thereby to decrease the bias of said spring as the force ex.- ertedby said contact member diminishes.

6. In an electromagnetic control device, a base, an electromagnet mounted upon said base, a rotatable switch shaft mounted upon said base, means attached to said shaft for supporting a magnetic armature for travel from a deenergized to an actuated position, a resilient contact member operable in conjunction with said shaft and arranged to engage a fixed contact when said armature is in said deenergized position, said contact member exerting a force tending to move said armature toward said actuated position, a radial supporting arm secured to said shaft in substantially parallel spaced relation to said armature, said arm carrying at its end a relatively short pivoted link, a helical tension spring pivotally connected to said pivoted link and to a fixed point on the opposite side of said switch shaft, said spring being arrangedto oppose the force of said contact member and to bias said armature to said deenergized position, said supporting arm being arranged to move the axis of said helical spring toward the center of said switch shaft as said armature approaches said actuated position, and a fixed stop mounted upon said baseto engage said pivoted link after said contact member and said fixed contact are disengaged and before said armature arrives at said actuated position thereby to decrease the tension of said spring as said armature completes its travel.

'7. In an electromagnetic circuit control device, an electromagnet mounted upon a base, a magnetic armature supported upon a fixed pivot on said base for travel from a deenergized to an actuated position, a resilient contact member operatively associated with said armature, said contact member being arranged resiliently to engage a fixed contact when said armature is in said deenergized position thereby to exert a force'tending to move said armature towardsaid actuated position, and a helical spring associated with said armature to overcome the force exerted by said contact member and to bias said armature to said deenergized position, the axis of said spring being arranged for movement toward said fixed pivot as said armature approaches said actuated position thereby to de-' crease the bias of said spring as the force exerted by said contact member diminishes, the relative strengths of said spring and said resilient contact member being so related that the resultant drop-out bias upon said armature increases gradually during the fir t portion of the travel of said armature away from said deenergized position.

8. In an electromagnetic circuit control device, an electromagnet mounted upon a base, a magnetic armature supported upon a fixed pivot on said base for travel from a deenergized to an actuated position, a resilient contact member operatively associated with said armature, said contact member being arranged resiliently to engage a fixed contact when said armature is in said deenergized position thereby to exert a force tend ng to move said armature toward said actuated position, a helical spring associated with said armature to overcome the force exerted by said contact member and to bias said armature to said deenergized position, the axis of said spring being arranged for movement toward said fixed pivot as said armature approaches said actuated position thereby to decrease the bias of said spring as the force of said contact member diminishes, the relative strengths of said spring and said resilient contact member being so related that the resultant drop-out bias upon said armature increases gradually during the first portion of the travel of said armature away from said deenergized position, and means controlled by the movement of said armature to stretch said spring after disengagement of said contact memberwith said fixed contact thereby rapidly to increase the resultant drop-out bias upon said armature during the last portion of its travel.

9. In an electromagnetic circuit control device, an electromagnet mounted upon a base, normally closed and normally open circuit controlling spring contacts, a magnetic armature supported. upon a fixed pivot upon said base for travel from a deenergized to an actuated position to open and to close said contacts respectively, said normally closed contacts being arranged resiliently to engage fixed contacts when said armature is in said deenergized position thereby to exert a force tending to move'said armature toward said actuated position, a helical spring associated with said armature to overcome the force exerted by said normally closed spring contacts and to bias said armature to said deenergized position, the axis of said helical spring being arranged for movement toward said fixed pivot as said armature approaches said actuated position thereby to decrease the bias of said spring as the force. exerted by said normally closed spring contacts diminishes, said normally closed spring contacts and said helical spring being so related that the resultant drop-out bias upon said armature increases gradually durin the initial portion of the travel of said armature toward said actuated position, and said normally open spring contacts and said helical spring being so related that the resultant drop-out bias upon said armature increases rapidly during the final portion of the closing travel of said armature.

10. In an electromagnetic circuit control device, an electromagnet mounted upon a base, normally open and normally closed circuit controlling spring contacts, a magnetic armature mounted upon a fixed pivot upon said base for travel from a deenergized to an actuated position to control said spring contacts, said normally closed spring contacts being arranged resiliently to engage fixed contacts when said armature is in said deenergized position thereby to exert upon said armature a force tending to move said armature toward said actuated position, a helical spring associated with said armature to overcome th force exerted by said normally closed spring contacts and to bias said armature to said deenergized position, a pivoted link for connecting said helical spring to said armature in such a for movement toward said fixed pivot as said armature approaches said actuated position thereby to decrease the bias of said spring as the force of said normally closed spring contacts diminishes, said normally closed spring contacts and said helical spring being so related that the resultant drop-out bias on said armature increases gradually during the initial portion of the travel of said armature toward said actuated position, and stop means mounted upon said base to engage said pivoted link during the final portion of the travel of said armature thereby rapidly to increase the drop-out bias applied to said armature.

11. In an electromagnetic circuit control device, a base, a-rotatable switch shaft mounted upon said base, a plurality of normally closed and a plurality of normally open spring contacts manner that the axis of said spring is arranged mally open spring contacts engaging second fixed contacts when said armature is in said actuated position thereby to exert a force tending to move said armature to said deenergized position, a radial supporting arm secured to said shaft in substantially parallel spaced relation to said armature, said arm carrying at its end a relatively short pivoted link, a helical tension spring pivotally connected to said pivoted link and a point on said base opposite said radial arm whereby the axis of said helical spring isarranged for movement toward the center of .said rotatable shaft as said armature moves toward said actuated position, said helical spring being arranged to oppose the force of said normally closed spring contacts and to bias said armature to said deenergized position, said normally closed spring contacts and said helical spring being so related that the resultant drop-out bias exerted upon said armature increases gradually during a predetermined initial portion of the travel of said arma-. ture toward said actuated position, and a fixed stop mounted upon said base to engage said pivposition.

WILLIAM LAWRENCE BUTLER. 

